@Cas tooMay be mistaken, but I think they're using "PTO" and "vacation" interchangeably here. "Unlimited PTO" essentially meaning there is no cap on how much vacation time you can accrue, and I guess at the caveat that you can't cash it out when you retire. As opposed to having a set cap of how much vacation you can accrue, any extra gets cashed out annually, and you get paid for any leftover when you retire.
To make things more confusing, I have both "Vacation" and "ATO". The former cash-able, the latter not.
Discussions likes this, one would think we're in the July off-season.
It means there's no bucket of PTO where hours are counted. There's nothing to cash out and there's nothing for the company to have to pay out should the employee and the company decide to part ways. At least in my case.